Method and device of calculating aircraft braking friction and other relating landing performance parameters based on the data received from aircraft&#39;s on board flight data management system

ABSTRACT

This invention relates to method and apparatus of the calculation of aircraft braking friction and other relating landing parameters including but not limited to aircraft braking action, aircraft takeoff distance, aircraft landing distance, runway surface conditions and runway surface friction based on the data collected by and available in the aircraft Flight Data Recorder (FDR) or other flight data management system for example the Quick Access Recorder (QAR) to provide every involved personnel in the ground operations of an airport and airline operations including but not limited to aircraft pilots, airline operation officers and airline managers as well as airport operators, managers and maintenance crews, the most accurate and most recent information on the true aircraft landing performance parameters to help better and more accurate safety and economical decision making.

BACKGROUND OF THE INVENTION

1. Field of invention

This invention relates to the method and the device of calculatingaircraft braking friction and other aircraft performance and pavementsurface characteristics parameters related to aircraft landing andtakeoff including but not limited to aircraft braking action, aircrafttakeoff distance, aircraft landing distance, runway surface conditionsand runway surface friction—from now on referred as true aircraftlanding performance parameters—based on the data collected or otherwiseavailable on board of an aircraft in electronic or other format from theaircraft Flight Data Recorder (FDR) or any other flight data providingor management system for example the Quick Access Recorder (QAR).

2. Background

Under severe winter conditions airlines, airports, civil aviationorganizations and countries rigorously impose limits on aircrafttakeoff, landing and other surface movement operations as well asenforce weight penalties for aircraft takeoffs and landings. Theselimits depend on the weather, runway and taxiway surface conditions andaircraft braking and takeoff performance. At the present these limitsare calculated from the assumed aircraft braking performance based onrunway conditions. These conditions are established by visualinspections, weather reports and the measurements of runway frictioncoefficient using ground friction measurement equipment.

At the present time, there are several practices to calculate theassumed aircraft braking performance:

1. The Canadian CRFI method:

The CRFI method comprises of a runway surface friction measurementperformed by braking a passenger vehicle traveling on the runway at acertain speed and measuring the maximum deceleration of it at severallocations along the length of the runway. The measured deceleration datais taken then and a braking index chart is used to calculate the assumedaircraft braking performance. The obtained aircraft landing performancedata and calculated assumed braking friction is provided to airlineoperators, pilots and airport personnel for decision making.

2. The reported runway friction coefficient by a runway frictionmeasurement equipment.

There are a great many number of runway friction measurement devicesmanufactured by different companies, in different countries and workingbased on different principles. Some of the most common devices are: (a)continuous friction measurement equipment (CFME); (b) decelerometers;(c) side force friction coefficient measurement equipment. Theseequipment are operated by airport operation personnel according to themanufacturer's instructions on the runways, aprons, and taxiways and themeasured friction coefficient is recorded. The recorded frictioncoefficient is then distributed to airline operation personnel, pilots,and airport personnel. The measured coefficient of friction is dependentof the measurement device, under the same conditions and on the samerunway different runway friction measurement devices based on differentprinciples will record different runway friction coefficients. Theserunway friction coefficients are assumed to relate to actual aircraftlanding and takeoff performance.

3. The new proposed IRFI method:

The International Runway Friction Index (IRFI) is a computational methodto harmonize the reported runway friction numbers reported by the manydifferent runway surface friction measurement equipments. The method wasdeveloped through an international effort with 14 participatingcountries. The method is a mathematical procedure based on simple linearcorrelations. The IRFI procedure is using a mathematical transformationto take the reported measurement of a runway friction measurement deviceand compute using simple mathematical methods an index called the IRFI.The mathematical procedures are the same for all the different runwayfriction measurement device using a different set of constant parametersthat was determined for each individual device. It is assumed that usingthis procedure the different runway friction measurement devicesreporting different friction coefficients can be harmonized. Thecalculated IRFI is assumed to correlate to aircraft landing and takeoffperformance.

4. Pre-determined friction levels based on observed runway conditions,current and forecasted weather conditions:

This method is available for airport operators according to newregulations. The method is based on airport personnel driving throughthe runway and personally observing the runway surface conditions. Theice, snow, water and other possible surface contaminants are visuallyobserved and their depth measured or estimated by visual observation.The estimated runway conditions with weather information are then usedto lookup runway friction coefficient in a table.

All these above mentioned practices are based on the measurement of therunway friction coefficient using ground friction measuring equipment,visual observation, weather information or combinations of these.However, according to present practices, there are several problems withthe measurement of the runway friction coefficient using these methods.

1. Need of a special device/car: there is a special car needed to beable to measure the runway friction coefficient. There are specialdevices to measure the runway friction coefficient that are commerciallyavailable; however, most of these devices are very expensive. Therefore,not every airport can afford to have one.

2. Close of runway: for the duration of the measurement the runway hasto be closed for takeoffs and landings as well as any aircraft movement.The measurement of the runway surface friction takes a relatively largeamount of time since a measuring device has to travel the whole lengthof the runway at a minimum one time but during severe weather conditionsit is possible that more than one measurement run is needed to determinerunway surface friction. The closing of an active runway causes thesuspension of takeoff and landing aircraft operations for a lengthenedperiod of time and therefore is very costly for both the airlines andthe airport. The using of ground vehicles to measure runway frictionposes safety hazard especially under severe weather conditions.

3. Inaccurate result due to lack of maintenance and inaccuratecalibration level: the result of the measurements are very dependent ofthe maintenance and the calibration level of measurement devices,therefore the result can vary much, and could loose reliability.

4. Confusing results due to the differences between ground frictiondevices: It has been established that the frictional values reported bydifferent types of ground friction measurement equipment aresubstantially different. In fact, the same type and manufacture, andeven the same model of equipment frequently report highly scatteredfrictional data. Calibration and measurement procedures are differentfor different types of devices. The repeatability and reproducibilityscatter or in other word uncertainty of measurements for each type ofground friction measurement device is therefore amplified and the spreadof friction measurement values among different equipment types issignificant.

5. Inaccurate result due to rapid weather change: Airport operationpersonnel, in taking on the responsibility of conducting frictionmeasurements during winter storms, find it difficult to keep up with therapid changes in the weather. During winter storms runway surfaceconditions can change very quickly and therefore friction measurementresults can become obsolete in a short amount of time, thusmisrepresenting landing and takeoff conditions.

6. Inaccurate result due to the difference between aircraft and theground equipment: It is proven that the aircraft braking frictioncoefficients of contaminated runways are different for aircraftscompared to those reported by the ground friction measurement equipment.

7. Inaccurate result due to the lack of uniform runway reportingpractices: For many years the international aviation community has hadno uniform runway friction reporting practices. The equipment used andprocedures followed in taking friction measurements varies from countryto country. Therefore, friction readings at various airports because ofdifferences in reporting practices may not be reliable enough tocalculate aircraft braking performance.

Therefore this invention recognizes the need for a system directlycapable of determining the true aircraft landing performance parametersbased on the data collected by and available in the aircraft Flight DataRecorder (FDR) or other flight data management systems. By utilizing thenovel method in this invention for the first time every involvedpersonnel in the ground operations of an airport and airline operationsincluding but not limited to aircraft pilots, airline operation officersand airline managers as well as airport operators, managers andmaintenance crews, will have the most accurate and most recentinformation on runway surface friction and aircraft braking action,especially on winter contaminated and slippery runways.

Utilizing this method the aviation industry no longer has to rely ondifferent friction reading from different instrumentations and fromdifferent procedures.

Therefore, this method will represent a direct and substantial benefitfor the aviation industry.

BRIEF SUMMARY OF THE INVENTION OBJECTIVE OF INVENTION

The objective of this invention is to provide every personnel involvedin the ground operations of an airport and involved in airlineoperations including but not limited to aircraft pilots, airlineoperation officers and airline managers as well as airport operators,managers and maintenance crews, the most accurate and most recentinformation on the true aircraft landing and takeoff performanceparameters to help in a better and more accurate safety and economicaldecision making, and to prevent any accident, therefore save lives.

BRIEF SUMMARY OF THE INVENTION

This unique and novel invention is based on the fact that most modemairplanes throughout the entire flight including the takeoff and landingmeasures, collects and stores data on all substantial aircraft systemsincluding the braking hydraulics, speeds and hundreds of otherperformance parameters. During the landing maneuver real time or afterthe aircraft parked at the gate this data can be retrieved, processedand the true aircraft landing performance parameters can be calculated.

During a landing usually an aircraft uses its speed brakes, spoilers,flaps and hydraulic and mechanic braking system and other means todecelerate the aircraft to acceptable ground taxi speed. The performanceof these systems together with many physical parameters including butnot limited to various speeds, deceleration, temperatures, pressures,winds and other physical parameters are monitored, measured, collectedand stored in a data management system on board of the aircraft (FIG.1).

All monitored parameters can be fed real time into a high poweredcomputer system that is capable of processing the data and calculatingall relevant physical processes involved in the aircraft landingmaneuver. Based upon the calculated physical processes the actualaffective braking friction coefficient of the landing aircraft can becalculated. This, together with other parameters and weather data, canbe used to calculate the true aircraft landing performance parameters(FIG. 6).

If real time data processing is not chosen, then the collected data fromthe aircraft can be transported by wired, wireless or any other meansinto a central processing unit where the same calculation can beperformed (FIG. 8).

The obtained true aircraft landing performance parameters data then canbe distributed to every involved personnel in the ground operations ofan airport and airline operations including but not limited to aircraftpilots, airline operation officers and airline managers as well asairport operators, managers and maintenance crews.

Utilizing the novel method in this invention for the first time everypersonnel involved in the ground operations of an airport and airlineoperations including but not limited to aircraft pilots, airlineoperation officers and airline managers as well as airport operators,managers and maintenance crews, will have the most accurate and mostrecent information on runway surface friction and aircraft brakingaction.

Utilizing this method, all the above mentioned (see BACKGROUND OF THEINVENTION) problems can be solved:

1. No need of a special device/car: this method uses the airplane itselfas measuring equipment, therefore no additional equipment needed. Moreover, no additional sensor needed. This method uses the readings ofpresent sensors and other readily available data of an aircraft.

2. No need for closing of runway: the duration of the measurement is thelanding of the aircraft itself. Therefore the runway does not have to beclosed.

3. No inaccurate result due to maintenance and the calibration level:because this method uses the aircraft itself as the measuring device,there is no variation due to the maintenance and the calibration levelof these ground friction measuring devices. The result of thecalculation will give back the exact aircraft braking friction theaircraft actually develops and encounters.

4. No inaccurate result due to the different between ground frictiondevices: because this method uses the aircraft itself as the measuringdevice, there is no variation due to the different ground frictionmeasuring devices.

5. Accurate result even in rapid weather change: As long as aircraftsare landing on the runway, the most accurate and most recent informationon the true aircraft landing performance parameters will be provided byeach landing.

6. No inaccurate result due to the difference between aircraft and theground equipment: because this method uses the aircraft itself as themeasuring device, there is no discrepancy in the measured and realfriction due to the difference between aircraft and the groundequipment.

7. No inaccurate result due to the lack of uniform runway reportingpractices: because this method uses the aircraft itself as the measuringdevice, there is no variation due to the difference reporting practices.

Utilizing this method the aviation industry no longer has to rely ondifferent friction readings from different instrumentations and fromdifferent procedures.

Therefore, this method represents a direct and substantial safety andeconomic benefits for the aviation industry.

The significance of this invention involves saving substantial amount ofmoney for the airline industry by preventing over usage of criticalparts, components of the aircraft including but not limited to brakes,hydraulics, and engines.

While increasing the safety level of the takeoffs, it could generatesubstantial revue for airlines by calculating the allowable take offweight, thus permissible cargo much more precisely.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

FIG. 1 Flight Data Recorder schematic: It is an illustration for thedata collection structure of the Flight Data Recorder (FDR).

FIG. 2 Example Pressure Altitude(ft) versus Time(s) data from the FlightData Recorder Data: It is a graphical illustration of the data from theFDR, which shows an example for the Pressure Altitude (ft) versusTime(s) during a landing.

FIG. 3 Example Brake Pressure (psi) versus Time (s) data from the FlightData Recorder Data: It is a graphical illustration of the data from theFDR, which shows an example the Brake Pressure versus Time(s) during alanding.

FIG. 4 Example AutoBrake setting versus Time (s) data from the FlightData Recorder Data: It is a graphical illustration of the data from theFDR, which shows an example the AutoBrake settings versus Time(s) duringa landing.

FIG. 5 A fraction of example data from the Flight Data Recorder: It isan illustration of the data from the FDR.

FIG. 6 The method of the calculation: The flow chart of the calculationsand comutations of the method

FIG. 7 An example for a friction limited braking: A graphicalpresentation of an example for a friction limited braking

FIG. 8 Post processing and distribution: It is an illustration of theschematic of the post processing and distribution.

FIG. 9 Real-time processing and distribution: It is an illustration ofthe schematic of the real-time processing and distribution.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1—This unique and novel invention is based on the fact that everyairplane during landing uses the hydraulics and braking system. During alanding usually an aircraft uses its speed brakes, spoilers, flaps andhydraulic and mechanic braking system and other means to decelerate theaircraft to acceptable ground taxi speed. The performance of thesesystems together with many physical parameters including but not limitedto various speeds, deceleration, temperatures, pressures, winds andother physical parameters are monitored, measured, collected and storedin a data management system on board of the aircraft. This figurepresents the schematics of the three major components of data sourcesonboard of an aircraft relevant to this invention, the measured andrecorded parameters related to the braking system, the measured andrecorded parameters to the engines, flight and other control systems ofthe aircraft, and the dynamic, external and environmental parametersmeasured and recorded.

FIG. 2—FIG. 5. This invention uses the sequence of data points recordedfrom the touch down of the aircraft until it reaches the normal taxiingspeed or comes to a stop. In the continuous data stream of the flightdata management system the touch down is marked by several events makingit possible to detect the beginning data point of the calculationprocess. From that point until the aircraft comes to complete stop atthe gate every necessary data points can be identified within therecorded data. FIG. 2 shows the recorded altitude measurements for anactual landing FIG. 3 depicts the measured the recorded hydraulicbraking pressures, FIG. 4 presents the recorded data for the auto-brakeselection and FIG. 5 illustrate the format of the recorded data that canbe obtained form a digital flight data management system.

FIG. 6—To arrive to the end result a number of different mathematicaland physical modeling approaches are possible through different sets ofdynamic equations and/or various methods of simulations based upon theavailability of different sets of data from the flight data managementsystem.

The following equations only represent an example of the possibleapproaches, and therefore the invention and the presented method is notlimited to these equations.

6.1—The following data is used as one of the possible minimum data setsfor the calculation, although more and/or different data can be utilizedto calculate the same parameters and/or improve the precision of thecalculation.

Data from the Flight Data Recorder: V_(air) Air Speed, P_(LB), P_(RB)Left and Right Brake Pressure, V_(ground) Ground Speed, A_(x)Longitudinal Acceleration, A_(c) Vertical Acceleration, E_(RPM) EngineRPM, S_(spolier) Spoiler setting, S_(airbrake) Airbrake setting,S_(aileron) Aileron setting, C_(flap) Flap configuration, C_(flap)θ_(pitch) Pitch, S_(RT) Reverse thrust setting S_(T) Engine thrustsetting

The following environmental data are used in the calculation. T_(air)Air Temp, P_(alt) Pressure Altitude, P_(air) Air Pressure, H_(%)Relative humidity, Δ_(Runway) Runway elevation

The following aircraft parameters are used in the calculation.M_(landing) Landing Mass, E_(type) Engine type, N_(engine) Number ofengines TY_(tire) Tire type TY_(aircraft) Aircraft type

6.2—The method calculates, through a three-dimensional dynamic model,all relevant physical processes involved in the aircraft landingmaneuver and separates them so they are individually available for use.The first intermediate result of the method is the time or distancehistory of all relevant, separated, interdependent decelerationsgenerated by the different systems in an aircraft. These decelerationsare cumulatively measured by the onboard measurement system and reportedin the flight data stream. The separated decelerations calculated fromthe different physical processes make it possible to calculate the truedeceleration developed only by the actual affective braking frictioncoefficient of the landing aircraft.

Based on the above, the software calculates the brake effectiveacceleration vs. time based on Equation (1).A _(Be) =A _(x) −A _(Drag) −A _(ReverseThrust) −A _(Rolling Resistance)−A _(Pitch)   (1)where A_(Be) is the brake effective acceleration

-   -   A_(x) is the measured cumulative longitudinal acceleration (6.1)    -   A_(Drag) is the deceleration due to the aerodynamic drag,        A _(Drag) =f(V _(air) , S _(spoiler) , S _(airbrake) , S        _(aileron) , C _(flap) , T _(air) ,P _(air) , H _(%) , M        _(landing) , TY _(aircraft))   (2)        where V_(air), S_(spoiler), S_(airbrake), S_(aileron), C_(flap),        T_(air), P_(air), M_(landing), TY_(aircraft), are parameters        from 6.1.    -   A_(ReverseThrust) is the acceleration caused by        thrust/reverse-thrust        A _(ReverseThrust) =f(E _(type) , N _(engine) , T _(air) , P        _(air) , H _(%) , E _(RPM) , S _(RT) , M _(landing) , TY        _(aircraft))   (3)    -   where E_(type), N_(engine), T_(air), P_(air), H_(%), E_(RPM),        S_(RT), M_(landing); TY_(aircraft), are parameters from 6.1    -   A_(RollingResistance) is the cumulative deceleration due to        other effects such us tire rolling resistance, runway        longitudinal elevation        A _(Rolling Resistance) =f(tire, V _(g) , M _(landing))   (4)    -   where tire, V_(g), M_(landing) are parameters from 6.1    -   A_(pitch) is due to the runway elevation        A _(Pitch) =f(Δ_(Runway))   (5)    -   where Δ_(Runway) is the runway elevation from 6.1.

This true deceleration (A_(Be)) developed only by the actual affectivebraking friction coefficient of the landing aircraft, than can be usedin further calculations to determine the true aircraft brakingcoefficient of friction.

6.3—Using the recorded data stream of the aircraft with the parametersindicated in point 6.1, plus weather and environmental factors reportedby the airport or measured onboard of the aircraft and thereforeavailable in the recorded data, together with known performance anddesign parameters of the aircraft available from design documentationand in the literature, the dynamic model calculates all relevant actualforces acting on the aircraft as a function of the true ground and airspeeds, travel distance and time. Using the results, the dynamic wheelloads of all main gears and the nose gear can be calculated.

Since the dynamic vertical acceleration of the aircraft is measured bythe onboard inertial instrumentation, the effective dynamic wheel load(N) can be calculated by the deduction of the calculated retardingforces by means of known aircraft mass; together with the determinedgravitational measurement biases introduced by runway geometry andaircraft physics using Equation 6 through 9.N=M _(Landing)·cos(θ_(pitch))·g−Lift−LoadTransfer−MomentumLift+g(A _(c),M _(loading))   (6)

Where

-   -   Lift is the computed force of the sum of all lifting forces        acting on the aircraft through aerodynamics:        Lift=f(V_(air) , S _(spoiler) , S _(airbrake) , S _(aileron) , C        _(flap) , T _(air) , P _(air) , H _(%) , M _(landing) , TY        _(aircraft))   (7)    -   where V_(air), S_(spoiler), S_(airbrake), S_(aileron), C_(flap),        T_(air), P_(air), H_(%), M_(landing), TY_(aircrft) are        parameters from point 6.1.    -   LoadTransfer is the load transfer from the main landing gear to        the nose gear due to the deceleration of the aircraft:        LoadTransfer=f(A _(Be) , M _(landing) , TY _(aircraft))   (8)    -   where A_(Be), M_(landing), TY_(aircraft) are parameters from        6.1.    -   MomentumLift is the generated loading or lifting forces produced        by moments acting on the aircraft body due to the acting points        of lift, thrust and reverse-thrust forces on the aircraft        geometry:        MomentumLift=f(S _(Thrust) , S _(RT) , C _(flap) , TY        _(aircraft))   (9)    -   where S_(Thrust), S_(RT), C_(flap),TY_(aircraft) are parameters        from point 6.1    -   g(A_(c), M_(landing)) is the dynamic force acting on the landing        gear due to the dynamic vertical movement of the aircraft, and        thus the varying load on the main gear due to the runway        roughness,    -   where A_(c), M_(landing) are parameters from point 6.1.

6.4—The deceleration caused by the wheel braking system of the aircraftcalculated in point 6.2 (A_(Be) is the true brake effectivedeceleration), together with the computed actual wheel load forcesacting on the main gears of the aircraft can be used to calculate thetrue braking coefficient of friction. First the actual true decelerationforce or friction force (F_(Fr)) caused by the effective braking of theaircraft have to be computed. From the brake effective deceleration(A_(Be)) obtained in 6.2 and the available aircraft mass, the methodcalculates the true effective friction force based on the formula:F _(Fr) =M _(landing) ·A _(Be)   (10)where M_(landing) is the landing mass of the aircraft from point 6.1 andA_(Be) is the calculated brake effective deceleration from Equation (1).

The determined true deceleration force (F_(Fr)) in equation 10 togetherwith the actual effective. dynamic wheel load (N) obtained in 6.3 can beutilized to calculate the true effective braking coefficient of frictionμ using equation 11:μ=F_(Fr)|N   (11)where

-   -   N is the calculated effective dynamic wheel force acting on the        tire (6.3),    -   and F_(Fr) is the friction force from Equation (10).

6.5—Using the calculated effective true frictional forces, together withparameters measured by the aircraft data management system (such asdownstream hydraulic braking pressure), a logical algorithm based on thephysics of the braking of pneumatic tires with antiskid braking systemswas designed to determine whether the maximum available runway frictionwas reached within the relevant speed ranges of the landing maneuver.

Together with the actual friction force the following logic is used bythis invention to determine:

(A) If friction limited braking is encountered.

If the actual available maximum braking friction available for theaircraft was reached by the braking system and even though moreretardation was needed the braking system could not generate because ofthe insufficient amount of runway surface friction a friction limitedbraking was encountered.

(B) If adequate friction for the braking maneuver was available,

If friction limited braking was not encountered and the braking waslimited by manual braking or the preset level of the auto-brake system,the adequate surface friction and actual friction coefficient can becalculated and verified.

6.6—In order to make sure that the auto-brake and antiskid systems ofthe aircraft were working in their operational range, the algorithm isanalyzing the data to look for the friction limited sections only in anoperational window where the landing speed is between 20 m/s and 60 m/s.

6.7—From the computed true effective braking coefficient of friction μcalculated in 6.4 the method computes the theoretically necessaryhydraulic brake pressure Pbrake and from the dynamics of the landingparameters an applicable tolerance is calculated t.

6.8—The data is analyzed for the deviation of the applied downstreamhydraulic brake pressure from the calculated theoretical brake pressurefrom 6.7 according to the obtained effective braking friction within theallowed operational window by the determined t tolerance. A sharpdeviation of the achieved and the calculated hydraulic braking pressureis the indication of friction limited braking. When sharply increasedhydraulic pressure is applied by the braking system, while nosignificant friction increase is generated, the potential of truefriction limited braking occurs.

FIG. 7—A graphical presentation for an example for the friction limitedbraking, where it can be seen that that a sharply increasing hydraulicpressure is applied by the braking system, while the friction isdecreasing. This is a very good example for a true friction limitedbraking.

The Different Applications of This Method

The Post Processing

FIG. 8—One possible approach in obtaining the true aircraft landingperformance parameters is a method of post processing. The data from theaircraft flight data management system is retrieved not real time butonly after the aircraft is finished its landing, taxiing and otherground maneuvers and arrived at its final ground position. The schematicof this approach is described in FIG. 8.

8.1—All monitored and available data is sent to the flight datamanagement system throughout the aircraft landing and ground maneuver.

8.2—Flight Data Management system collects, processes and stores theretrieved data in a data storage. The data storage is in fact part ofthe Flight Data Management system where all the data is stored.

8.3 Data transfer—After the airplane stopped at the gate or otherdesignated final position, the collected data from the aircraft can betransported by wired, wireless or other means into a central processingunit.

8.4 High Power computer—All recorded parameters transported from theaircraft can be fed into a computer system, which is capable ofprocessing the data and calculating/simulating all relevant physicalprocesses involved in the aircraft landing maneuver and the actualaffective braking friction coefficient of the landing aircraft and thetrue aircraft landing performance parameters can be computed and madeready for distribution.

8.5 Data Distribution—The computer distributes the calculated truelanding parameters to other interested parties through wired, wirelessor other data transportation means. Real-time data processing

FIG. 9—In the case of real time data processing, all monitoredparameters can be fed real time into an onboard high power computersystem that is capable of processing the data and calculating allrelevant physical processes involved in the aircraft landing maneuver.Based upon the calculated physical processes the actual affectivebraking friction coefficient of the landing aircraft can be calculated.This together with other parameters and weather data can be used tocalculate the true aircraft landing performance parameters. In case thecalculation finds a true friction limited section, a warning can be sentto the pilot to prevent any accident, such as over run or slide off therunway.

9.1—All monitored and available data is sent to the flight datamanagement system throughout the aircraft landing and ground maneuver.

9.2—Flight Data Management system collects, processes and stores theretrieved data in a data storage. The data storage is in fact part ofthe Flight Data Management system where all the data is stored.

9.3—High power computer system: All monitored parameters fed real timeinto a this computer system, which is capable of processing the data andcalculating/simulating all relevant physical processes involved in theaircraft landing maneuver and the actual affective braking frictioncoefficient of the landing aircraft and the true aircraft landingperformance parameters.

9.4—Pilot warning: Based on the calculated aircraft braking coefficientand the method to search for friction limited braking it gives a warningin case the friction is too low or continuously informs the driver ofthe generated and available braking and cornering coefficient offriction.

9.5—Distribution: The onboard computer distributes the calculated truelanding parameters to other interested parties.

Significance of the Invention

Utilizing the novel method in this invention for the first time allpersonnel involved in the ground operations of an airport as well asairline personnel involved in operations including but not limited toaircraft pilots, airline operation officers and airline managers as wellas airport operators, managers and maintenance crews, will have the mostaccurate and most recent information on runway surface friction andaircraft braking action.

Utilizing this method the aviation industry no longer has to rely ondifferent friction readings from different instrumentations and fromdifferent procedures or assumed friction levels based on visualobservation and weather data.

Therefore, this method represents a direct and substantial safety andeconomic benefits for the aviation industry.

Econonmic Benefits

The significance of this invention involves knowing the true aircraftlanding performance parameters for landing which yields substantialfinancial savings for the airline industry. While increasing the safetylevel of the takeoffs, it could also generate substantial revenue forairlines.

Therefore a system directly capable of determining the true aircraftlanding performance parameters would represent direct and substantialeconomic benefit for the aviation industry including but not limited to:

-   -   1. Preventing over usage of critical parts, components of the        aircraft including but not limited to brakes, hydraulics, and        engines.    -   2. The distribution of the calculated parameters for the airport        management helps making more accurate, timely and economic        decisions including but not limited to decision on closing the        airport or decision on the necessary maintenance.    -   3. The calculated parameters reported to the airline management        yields more accurate and economic decision making including but        not limited to permitting the calculation of allowable take off        weights much more precisely thus increasing the permissible        cargo limits.        Safety Benefits

The significance of this invention involves the precise assessment ofthe true runway surface characteristics and aircraft braking and landingperformance by providing the true aircraft landing performanceparameters. This is fundamental to airport aviation safety, andeconomical operations especially under winter conditions and slipperyrunways. Thus, a system directly capable of determining the trueaircraft landing performance parameters real-time and under anyconditions without restricting ground operations of an airport wouldrepresent direct and substantial safety benefit for the aviationindustry including but not limited to:

-   -   1. Providing real-time low friction warning to help pilots to        make critical decisions during landing or take-off operations to        prevent accidents, costly damages or loss of human lives.    -   2. Eliminating the confusion in the interpretation of the        different Ground Friction Measuring Device readings and        therefore giving precise data to airport personnel for critical        and economical decision making in airport operations and        maintenance.    -   3. Giving an accurate assessment of the actual surface        conditions of the runway, that could be used in the aircraft        cargo's loading decision making for safer landing or take-offs.    -   4. Providing accurate data for distribution to airport        management personnel assisting them in more accurate, timely and        safe decision making.    -   5. Providing data to be reported to pilots about to land for        safer and more accurate landing preparation.    -   6. Providing data to be reported to pilots about to take off for        safer and more accurate takeoff preparation    -   7. It could be reported to the airline management to for more        accurate safety decision making

1. A method of a calculation to determine real-time or by postprocessing the true aircraft braking friction coefficient based on thedata collected by and available in the aircraft flight data managementsystems such as the Flight Data Recorder (FDR).
 2. A method of acalculation to determine real-time or by post processing, based upon themethod in claim 1, other relating parameters including but not limitedto aircraft braking action, aircraft cornering friction coefficient,aircraft takeoff distance, aircraft landing distance, runway surfaceconditions and runway surface friction.
 3. An apparatus onboard of theaircraft to give a real-time low braking action warning to help pilotsto make critical decisions during landings and takeoffs based on themethod in claim 1
 4. An apparatus for calculating all the parameters inclaim 1 and 2 onboard of the aircraft to help pilots to make criticaldecisions during landings and takeoffs based on the method in claim 1.